How sovereign is the United Kingdom?

To address the issue of whether the United Kingdom has retained its sovereignty requires a number of points to be examined. First, in 2006, what exactly is 'sovereignty' within a nation?

If your definition is xyz, and Europe is seen to be trespassing on these, then by your definition, our sovereignty is being undermined.

However, by how much? Is one of the eight following statements trespassed on? Or is it just slightly trespassed on? If it is five, is this a lot? Is just one, the thin end of the wedge  the start of things to come?